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different juices from the common mass. The fame holds allo with regard to the capillary vessels (a) of vegetables, ic being evident that through the fine trainers in the leaves and all over the body of the plant, there be juices or Auids of a particular kind drawn in, and separated from the common mass of air and light. And that the most claborate spirit, whereon the character or diftin. guishing virtue and properties of the plant depend, is of a luminous (b) and volatile nature, being loft or escaping into air or æther, from effential oils and odoriferous waters, without any sensible diminution of the subject. .
216. As different kinds of secreted light or fire produce different essences, virtues, or specific properties, so also different degrees of heat produce different effects. Thus one degree of heat keeps the blood from coagulating, and another degree coagulates the blood. Thus a more violent firę hath been observed to fee free and carry off that very light, which a more moderate fire had introduced and fixed in the calcined regulus of antimony. In like' manner, one kind or quantity of this ætherial fiery spirit may be congenial and friendly to tho spirits of a man, while another may be noxious...
217. And experience sheweth this to be true, For the fermented spirit of wine or other liquors procuçeth irregular motions, and fubsequeni depressions in the animal spirits. Whereas the lu. minous fpirit lodged and detained in the native bal. fam of pines and firs, is of a nature so mild and benign and proportioned to the human constitution, as co warm without heating, to cheer but not ino
(a) 39, 31, 33, 35,-: , (W) 376 43.
briate, and to produce a calm and steddy joy like the effect of good news, without that sinking of spirits which is a subsequent effect of all fermented cordials. I may add, without all other inconvenience, except that it may like any other medicine be taken in too great a quantity for a nice stomach. In which case it may be right, to lessen the dose, or to take it only once in the four and twenty hours, empty, going to bed (when it is found to be leaft offensive) or even to suspend the taking of it for a time, till nature shall seem to crave it, and rejoice in it's benign and comfortable spirit..
218. Tar-water serving as a vehicle to this spirit is both diuretic and diaphoretic, but seems to work it's principal effect by affisting the vis vitæ, as an alterative and cordial, enabling nature by an accession of congenial spirit, to assimilate that which could not be assimilated by her proper force, and so to subdue the fomes morbi. And this should feem in most cases the best and safest course. Great evacuations weaken nature as well as the disease. And it is to be feared that they who use salivations and copious bleedings may, though they should recover of the distemper, in their whole life be neyer able to recover of the remedies.
219. It is true indeed, that in chronical cases there is need of time to compleat a cure, and yet I have known this tar-water in disorders of the Jungs and stomach to prove a very speedy remedy, and to allay the anxiety and heat of a fever in an instant, giving ease and spirits to the patient.
This I have often experienced, not without surprise at seeing these falutary effects follow so immediately in a fever on taking a glass of tar-water, Such is the force of these ačtive vivifying princi. ples contained in this balsam,
220. Force or power, strictly speaking, is the agent alone who imparts an equivocal force to the invisible elementary fire, or animal Spirit (a) of the world, and this to the ignited body or visible flame, which produceth the sense of light and heat. In this chain the first and last dioks are allowed to be incorporeal: the two intermediate are corporeal, being capable of motion, rarefaction, gravity, and other qualities of bodies. It is fit to distinguish these things, in order to avoid ambiguity concerning the nature of fire.
221. Sir Isaac Newton in his Optics, asks; Is pot fire' a body heated fo hot as to emit light copioufly ? for what else, adds he, is a red hot iron than fire? Now it should feem, that to de. fine fire by heat, would be to explain a thing by it felf.. A body heated fo hot as to emit light is an ignited body, that is, hach fire in it, is penetraLed and agitated by fire, but is not it felf fire. And although it fhould in the third foregoing acceptation, or vulgar fenfe pass for fire, yet it is not the pure elementary (b) fire in the second or philofophic fenfe, such as was understood by the fages of antiquity, and fuch as is collected in the focus of a burning glafs ; much less is it the vis, force, or power of burning, destroying, calcining, melting, vitrifying and raifing che perceptions of light and heat. This is truly and really in the incorporeal agent, and not in the vical spirit of the univerfe. . Morion, and even power in an .cquivocal ifense, may be found in this pure ætherealfpirit, which ignites bodies, but is not itself she ignited' body, being an inftrument or medium fe) by which the real agent doch operate on groffer bodies. . . . . (a) 153, 156, 157 (0) 190. (0) 160.
1. 222. It hach been shewed in fir Isaac News ton's Optics, that light is not reflected by imping, ing on bodies, but by some other cause. And to him it seems probable, chat as many rays as impinge on the solid parts of bodies, are not re flected but stifted and retained in the bodies. And it is certain, the great porosity of all known bodies affords room for much of this light or fire to be lodged therein, Gold it self the most solid of all metals, seems to have far more pores than folid parts, from water being pressed through it in the Florentine experiinent, from magnetic effluvia paffing, and from mercury entering its pores fa freely. And it is admitted that water, though ima poffible to be compressed, hath at least forty cimes more pores than folid parts. And as acid pars ticles, joined with those of earth in certain proportions, are so closely united with them, as ca be quite hid and loft to all appearance, as in mercurius dulcis and common fulphur, fo also may we conceive the parcicles of light or fire to be absorbed and latent in groffer bodies.
223. It is the opinion of fir Ifaac Newton, that somewhat unknown remains in vacuo, when the air is exhausted. This unknown medium he calls: æther. He supposech it to be more fubtil in irg: nature, and more swift in its motion, than light, freely to pervade all bodies, and by its immensei clasticity to be expanded throughout all the heae, vens. Its density is fuppofed greater in free and. open spaces, than within the pores of compact bodies. And, in paffing from the celestial bodies to great distances, it is supposed to grow denser and denser continually ; and thereby. cause thoset great bodies to gravitate towards one anocher, and their respective parts towards their centers, every
body endeavouting to pass from the denser parte of the medium towards the rarer. [ 224. The extreme minuteness of the parts of this medium and the velocity of their motion, together with its gravity, density, and elastic force, are thought to qualify it for being the cause of all the natural motions in the universe. To this cause are afcribed the gravity and cohesion of bodies. The refraction of light is also thought to proceed, from the different density and elastic force of this ætherial medium in different places. The vibrations of this medium alternately concurring with, or obstructing the motions of the rays of light, are supposed to produce the fits of easy reflexion and transmission. Light by the vibrations of this medium is thought to communicate heat to bodies, Animal motion and sensacion are also accounted for by the vibrating motions of this ætherial medium, propagated through the solid capillaments of the nerves. In a word, all the phænomena and properties of bodies, that were before attributed to attraction, upon later thoughts seem ascribed to this æther, together with the various attractions themselves. · 225. But in the philosophy of fir Isaac Newton, the fits (as they are called) of easy transmission and reflexion, seem as well accounted for by vibrations excited in bodies by the rays of light, and the refraction of light by the attraction of bodies. To explain the vibrations of light by those of a more subtil medium, seem an uncouch explication. And gravity seems not an effect of the density and elafticity of acher, but rather to be produced by some other cause ; which fir Isaac himself insinuates to have been the opinion even of those ancients who took vacuum, atoms, and the gravity of atoms for the principles of their philosophy, tacitly attri